Grinding wheel speed regulator



June 16, 1953 R, G, KIRBY ETAL 2,641,875

' GRINDING WHEEL SPEED REGULATOR Filed Sept. 26, 1951 3 Sheets-Sheet 1 www/.fm

l TTORNEYS R. G. KIRBY ETAL June 16,1953

GRINDING WHEEL SPEED REGULATOR 3 Sheets-Sheet 2 Filed Sept. 26,- 1951 June 16, 1953 R. G. KlRY ETAL GRINDING WHEEL SPEED REGULATOR Filed se'pm 2s. 1951 3 Sheets-Sheet 5 W Jui 111|.. u n w- -T :Y @I 9 Mb r Q j n 4 9 l ....rll 7 u ...w f 6.--- f/.z W l N 7 y d A 4 7 n nd\ 3 7 f a xl. il v\ u m 1 f 0, l G s Cm m \Umwa Patented June 16, 1953 GRINDING WHEEL SPEED REGULATOR -Roy G. Kirby, John M. Morgan, Jr., and Jacob v Ohio, assignors to The Decker, Cincinnati,

Cincinnati Milling Machine Co.,

Cincinnati,

Ohio, a corporation of Ohio Application September 26, v1951, Serial No. 248,366

6 Claims.

This invention relates to grinding machines and more particularly to mechanism for automatically regulating the speed of the grinding Wheel in accordance with decrease in the size thereof. It is well known in the art of grinding that grinding wheels gradually wear away in the course of grinding operations, thereby reducing their diameter, and that further reductions in diameter are effected by the intermittent dressing or truing operations.

Since grinding wheels are usually coupled by a constant speed mechanism to their driving motors, the gradual reduction in the size of the wheel decreases `the peripheral speed of the grinding face of the wheel. It is many times desirable, however, that to obtain the best grinding results that the speed of the grinding face remain substantially` constant. Attempts have been made in the past at regulating the speed of the grinding wheel, but this has always dependedy upon the operator to make certain adjustments to accomplish the desired results. By means of this invention the operator does not have to give any thought regarding the speed of the wheel because the adjustment is made automatically each time that the grinding wheel is stopped. This invention contemplates the use of a device which is mounted on a Xed support adjacent the wheel and having a part which will engage the wheel each time it is stopped to ascertain the amount of wheel reduction since the previous determination and automatically effect a change in the speed of the driving motor the next time it is started.

Referring to the drawings in which like referen-ce numerals indicate like or similar parts:

Figure l is an elevational view partly in section showingrthe grinding wheel supporting elements with the speed compensating mechanism mounted on the wheel housing.

Figure 2 is a view on the line 2-2 of Figure 1.

Figure 3 is a View on the line 3 3 of Figure 1.

Figure 4 is a view on the line 4 4 of Figure 2.

Figure 5 is a diagram of the control circuit.

Referring to Figure 1, the reference numeral I indicates generally a grinding wheel spindle housing of conventional design which is slidably mounted on a pair of guideways, one of which is indicated'by the reference numeral I I formed on the bed 'I2 of a grinding machine. The grinding wheel spindle is indicated by the reference numeral I3, and this may be operatively connected in the usual manner to a driving motor I4 as shown in Figure 5, mounted on the spindle housing I0. One or more grinding wheels I are 2. shown attached to the end of the spindle in Figure 1 and clamped thereon between the iianges I6 and Il. Thus, rotation of the spindle will impart rotation to the grinding wheel.

The driving motor I4, shown in Figure 5, is

electrically connected by wires contained in the conduit pipe I8 to a rotatable speed control potentiometer I9 whereby the rotatable position of the potentiometer determines the speed of rotation of the motor I4. A pair of wires and 2I extend from the junction box 22 to switches 23 and 24 of a motor starting relay having an operating coil 25. By energizing the relay 25 the switch contactors 26 and 2l close, thereby connecting the line 2i) to one power main 28 and the other line 2| to the power main 29. These power mains may receive power from one side of a transformer indicated generally by the reference numeral 30 in the usual manner. y

Before the starter relay 25 can be operated, it is necessary that pressure exist in a hydraulic system, part of the oil from which is utilized for lubricating purposes, and part utilized for operating the speed control mechanism. The hydraulic system, shown in Figure 5J has a pump diagrammatically indicated by the reference 11unmeral 3|, and this pump is driven by an electric motor 32 which has apair of leads 33 and 34 extending to starter switches 35 Vand 36. These switches are closed by a relay coil 31 thereby the lead 34 is connected to the power line 29 and lead 33 is connected to the power line 28. One end 38 of the relay coil 31 is connected to the power line 28. The other end 39 of the relay coil is connected to a contact 40 of a push button starting switch 4I. When this switch is closed by the operator, the relay '39 is energized, and the pump 3l vis set into operation.

This pump has an intake 42 through which fluid is withdrawn from a reservoir 43 and delivered into a line 44 having a check valve 45 through which the fluid passes into line 46. This vmotor.

line has two branches 41 and 48, the branch l1 leading to a pressure switch indicated generally by the reference numeral 48 whereby when the necessary pressure has been established the switch will close and complete a circuit from the power line 29 through the normally closed stop switch 49, line 50, line 5I which is connected to line 511 by the operator holding the starting switch closed, closed switch 138 and line 52 to the starter relay coil 25 for the grinding wheel On the other hand, however, as soon as the starting switch 4I is closed, a holding circuit is established to the pump starter relay 3'I,`be

cause as soon as it is energized a third contactor 53 is closed by the relay, establishing a holding cir-cuit from the line 58 through the line 54, closed switch 53 and line 55 to the relay 39. When the pump 3i has built up sufficient pressure to close the pressure switch 48, a circuit is established to the motor starting relay as just described, and, in turn, this will close conductor 56, in addition to the switches 23`and 24 and establish a holding circuit for the relay 25 from line 55 through line 5l', closed switch 58, line 58 to the closed pressure switch 48 and then through line 52 to the relay 25.

At the same time that pressure is created in the branch 4T, pressure is also built up in the branch line 48, and this line terminates in a cylinder 59 having a piston B8 which is operatively connected by means of piston rod '53, arm 'l2 and shaft 85 to a feeler arm 8l. This arm has a roller 62 journaled in the end thereof for contact with the periphery of the grinding wheel. When no pressure exists in the cylinder 59 the roller 62 is normally held in contact with the periphery of the grinding wheel by a spring 83 which has one end attached to the arm 'l2 and the other end attached to a fixed pin 64. Since it takes more pressure to operate the pressure switch 48 than it does to actuate the piston 58, it will be obvious that the roller 82 will be raised out of contact with the grinding wheel before the wheel -is rotated by its driving motor I4. This eliminates Wear on the roller.

The feeler arm 6l, as shown in Figure 4, is keyed at 65 to operating shaft 68 which is journaled at opposite ends in bearing blocks 9'! and 68 secured to supporting plates 8'! and '18. These plates are suitably attached to the grinding wheel housing, indicated generally by the reference numeral 1l. The arm 'I2 has a bore 73 by which the arm is mounted on the shaft and the end of the arm is bifurcated as indicated at '14 in Figure 2 by which it may be secured by a clamp screw 'l5 to the shaft for rotation therewith. This arm is the one that is connected to the piston rod 13 of the piston 89 for imparting rotation to the shaft 85 and the feeler arm Si. The shaft 8'5 has another arm 'I8 attached thereto as shown in Figure l in the same manner as the arm l2, and this arm is in the form of a gear quadrant, indicated by the reference numeral 11, which meshes with a pinion 18 attached to the potentiometer I9 and imparts rotation thereto upon rotation of the quadrant '17.

Referring now to Figure 3, the shaft G6 has another member attached thereto in the form of a ratchet plate 19. This ratchet plate has a bore and a bifurcated end 88 which intersects the bore so that by means of the clamping screw 8l the ratchet plate may be secured for rotation with the shaft whenever the same is rotated. Referring to Figure 4, a pawl carrier plate 82 is supported for free rotation between the ratchet plate 19 and the bearing block 68 and is held in position by a anged plate 83 which is secured to the bearing block 88 by screws 84. The pawl carrier plate 82 has a small hole 84 drilled therein, as shown in Figures 3 and 4, and a fixed pin 85 mounted in the bearing block 88 projects into the hole with a limited amount of lost motion. Thus, the plate 82 has a very limited rotation which is determined by the amount of lost motion between the fixed pin 85 and the hole 84. A spring 88 is attached at one end to a pin 81 projecting from the plate 82, and at the other end to an adjusting screw 88 which is threaded in a fixed lug 89 projecting from the plate 10 as shown in Figure 4. By adjusting the tension of the spring 86, the pawl carrier plate 82 may be held in contact with the pin 85.

The plate 82 carries two pawls 90 and 9| which are pivotally mounted on pins 92 and 93 carried by the plate 82. These pawls engage the teeth on the periphery of the ratchet plate 19 and limit the return movement of the ratchet plate. In other words, when the feeler arm 6| rotates the shaft '66 in a clockwise direction, as Viewed in Figure 3, the ratchet plate 19 also moves in a clockwise direction until the feeler roller engages the periphery of the grinding wheel. Since the pawl carrying plate 82 cannot move in this direction at this time because of its engagement with the Xed pin 85, the ratchet teeth will slip ahead of the ratchet pawls. However, when the hydraulic pressure is admitted to the cylinder 59 and the piston 68 rotates the shaft 66 in a counterclockwise direction as viewed in Figure 3, the ratchet plate will, through interaction with one or the other of the pawls, cause rotation of the plate 82 .by the amount of the lost motion between the fixed pin and the hole 84. The amount of this lost motion determines the distance that the feeler roller will be raised out of engagement with the periphery of the grinding wheel. It will thus be apparent that no matter how far the feeler roller advances in a clockwise direction its return movement will always be limited by the amount of lost motion between the pin 85 and the hole 84.

It is to be noted that the potentiometer will be advanced and retracted with the feeler arm, but due to wear of the wheel this advance movement will be greater than the return movement whereby the potentiometer will be gradually advanced and, as it does so, it gradually increases the speed of the motor and thereby of the grinding wheel.

When the grinding wheel is worn out, and it becomes time to change the wheel, the pawls are moved out of engagement with the ratchet plate by means of an arm 93 which is freely pivoted on the pin 92. By raising this arm it engages pins 94 and 95 projecting respectively from pawls 98 and 9|, thereby raising the pawls out of engagement with the ratchet plate. The feeler arm 6I is then raised until a spring latch 96 engages a hole 91 formed in the upper part of the arm 6I and thereby holds it in a raised position. After the wheel has been changed, the arm is released and moved into contact with the periphery of the new wheel.

It will be noted from Figure 5 that the branch line 48 which supplies fluid pressure to the cylinder 59 has a branch resistan-ce coil 98 connected thereto through which oil from the line 48 is bled off to reservoir. The purpose of this is that when the machine is stopped, and the pump 32 shut down, that the oil will not immediately leave the cylinder 59 but will slowly bleed therefrom, thus allowing time for the grinding wheel to coast to a stop before the roller 62 engages the periphery of the Wheel.

It is believed that the operation of the mechanism will be clearly understood from the foregoing description and that further description of the operation of the device is not necessary.

There has thus been provided an improved mechanism for automatically controlling the speed of the grinding wheel as it wears down without attention from the operator and that the peripheral face of the wheel will be mainjustable speed control means for said motor in- Y cluding a feeler arm movable into and out of engagement with the face of said wheel, a stop mechanism for limiting the retrograde movement of said arm including a ratchet plate rotatable with said arm, and stop pawls engageable with said plate for limiting the retrograde movement of said arm.

2. In a grinding machine having a grinding wheel spindle supporting a grinding wheel for rotation thereby, the combination with a variable speed motor for rotating said spindle at prescribed rates in accordance with the diameter of said wheel, of rate control means for determining the speed of said motor, a feeler arm operatively connected to said rate control means and supported for movement toward and from the periphery of the grinding wheel, spring means for moving said arm into engagement with said wheel, and poweroperable means for disengaging said arm whenever the motor is energized.

3. In a, grinding machine, the combination of means for regulating the speed of the grinding wheels in accordance with the diameter thereof including a feeler arm for engaging said wheel, means normally holding said arm in engagement with said wheel, a power operable motor for rotating said wheel including a control circuit energizable for starting said motor, and means responsive to energization of said circuit to eiect disengagement of said arm from the grinding wheel before the motor begins rotation.

4. In a grinding machine, the combination of means for regulating the rate of rotation of the grinding wheel in accordance with the diameter thereo including a power operable motor for rotating said wheel, rate control means for said motor settable by a feeler arm normally in engagement with said wheel when Kthe motor is stopped, power operable means to eiect disengagement of said arm, a control circuit for energizing said power operable means and said motor, stop means for limiting the disengaging movement of said arm and thereby determining the setting of said rate control means, and means responsive to deenergization of said'circuit for delaying return of said arm until the grinding wheel has stopped.

5. In a grinding machine having a grinding Wheel spindle supporting a grinding wheel for rotation thereby, the combination with a variable speed motor for rotating said spindle to impart a predetermined peripheral speed to said grinding wheel, of a potentiometer operatively connected for determining the speed of said motor, a feeler arm movable into engagement with said Wheel and operatively connected to said potentiometer for positioning thereof in accordance with movement of the arm, fluid pressure control means automatically operable to move the arm out of engagement with said wheel and set said potentiometer, a starting switch for said motor operable by said uid pressure means to actuate said motor at the speed set by said potentiometer, and means to release said fluid pressure means to stop the motor and return the arm into engagement with said Wheel.

6. In a grinding machine having a motor for eiecting rotation of the grinding wheel thereof, the combination with a rate control means for said motor, of a feeler arm connected to said rate control means and movable into and out of engagement with said grinding wheel, fluid pressure control means for automatically moving the arm out of engagement with said wheel, a starting switch for said motor operable by said uid pressure means to eiect actuation of said motor, a ratchet stop mechanism operatively connected to said arm for limiting the retrograde movement of said arm to a predetermined amount and thereby the motor speed setting of said rate control means whereby when the advance movement of said arm is greater due to wheel wear .than the constant retrogade movement, the rate control means will be automatically adjusted to increase the rate of rotation of said motor.

ROY G. KIRBY.

JOHN M. MORGAN, JR. JACOB DECKER.

References lcited in the fue of this patent UNITED sTATEs PATENTS Number Name Date 766,229 Douglas Aug. 2, 1904 2,056,871 Silven Oct. 6, 1936 2,302,304 Elberty Nov. 17, 1942 2,545,730 Fouquet Mar. 20, 1951 

